I'm not entirely sure. I don't think there was a McDonald's nearby, but there was a Starbucks. I do remember reading before the 3DS released that there would be special hotspots located around the place.

It was the Fashion Show mall, which is a pretty major one on the LV strip.

Been scouting ebay for a second hand 3DS and most of them are offering Amaze Cards or other flash cards. This is not something I am particularly interested in, but would it mean that the console would be limited/non standard with its online functionality as a result of the previous owner?

Nintendo announced when 3DS launched that it'd contain some sort of information to let them know if you'd used a flash card and that if you went online you'd risk bricking your console. So yeah, I'd stay away.

I know this is hardly conclusive, but after reading this I feel somewhat vindicated for being skeptical of what everyone claimed was an "inevitable" 3DS redesign.

I could still end up being wrong about this, but I just don't think Nintendo will revise the 3DS like they did (multiple times) with the DS. Nintendo just doesn't seem to view the lack of a second analogue stick as a "mistake", either, like so many others do, and I'm kinda with the company on that one.